#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#include <uv.h>

typedef struct {
  uv_write_t req;
  uv_buf_t buf;
} write_req_t;

uv_loop_t* loop;
uv_pipe_t stdin_pipe;
uv_pipe_t stdout_pipe;
uv_pipe_t file_pipe;

void alloc_buffer(uv_handle_t* handle, size_t suggested_size, uv_buf_t* buf) {
  (void)handle;
  *buf = uv_buf_init((char*)malloc(suggested_size), suggested_size);
}

void free_write_req(uv_write_t* req) {
  write_req_t* wr = (write_req_t*)req;
  free(wr->buf.base);
  free(wr);
}

void on_stdout_write(uv_write_t* req, int status) {
  (void)status;
  free_write_req(req);
}

void on_file_write(uv_write_t* req, int status) {
  (void)status;
  free_write_req(req);
}

void write_data(uv_stream_t* dest, size_t size, uv_buf_t buf, uv_write_cb cb) {
  write_req_t* req = (write_req_t*)malloc(sizeof(write_req_t));
  req->buf = uv_buf_init((char*)malloc(size), size);
  memcpy(req->buf.base, buf.base, size);
  uv_write((uv_write_t*)req, (uv_stream_t*)dest, &req->buf, 1, cb);
}

void read_stdin(uv_stream_t* stream, ssize_t nread, const uv_buf_t* buf) {
  (void)stream;
  if (nread < 0) {
    if (nread == UV_EOF) {
      // end of file
      uv_close((uv_handle_t*)&stdin_pipe, NULL);
      uv_close((uv_handle_t*)&stdout_pipe, NULL);
      uv_close((uv_handle_t*)&file_pipe, NULL);
    }
  } else if (nread > 0) {
    write_data((uv_stream_t*)&stdout_pipe, nread, *buf, on_stdout_write);
    write_data((uv_stream_t*)&file_pipe, nread, *buf, on_file_write);
  }

  // OK to free buffer as write_data copies it.
  if (buf->base)
    free(buf->base);
}

int main(int argc, char** argv) {
  (void)argc;
  loop = uv_default_loop();

  uv_pipe_init(loop, &stdin_pipe, 0);
  uv_pipe_open(&stdin_pipe, 0);

  uv_pipe_init(loop, &stdout_pipe, 0);
  uv_pipe_open(&stdout_pipe, 1);

  uv_fs_t file_req;
  int fd = uv_fs_open(loop, &file_req, argv[1], O_CREAT | O_RDWR, 0644, NULL);
  uv_pipe_init(loop, &file_pipe, 0);
  uv_pipe_open(&file_pipe, fd);

  uv_read_start((uv_stream_t*)&stdin_pipe, alloc_buffer, read_stdin);

  uv_run(loop, UV_RUN_DEFAULT);
  return 0;
}
